KR102333192B1 - Inverter using microcontroller - Google Patents

Abstract

An inverter using a microcontroller is disclosed. An inverter using a microcontroller includes a buck element, an inductor having one end connected to an output voltage pin of the buck element, a first diode having one end connected to an output voltage pin, and a first capacitor having the other end of the inductor connected to a positive pole. , a first connection point formed by connecting the other side of the inductor and the positive pole of the first capacitor, a ground pin of the buck element, a second connection point formed by connecting the other side of the first diode and the negative pole of the first capacitor, a second connection point a second diode having one side connected to the , the other side connected to the ground, a collector connected to the first connection point, a transistor having an emitter connected to the ground, and a first output with the base of the transistor a microcontroller connected by a pin and connected to the first connection point and the second connection point by a first input pin and a second input pin, respectively, wherein the microcontroller is configured to: 1 Controls the switching of the transistor through the output pin.

Description

Inverter using microcontroller

The present invention relates to a power circuit provided in an electronic device, and more particularly, to an inverter using a microcontroller provided to supply power to an electronic device.

All electronic devices have a power supply circuit as an essential component. That is, in order for the electronic device to operate, a power supply circuit for supplying power suitable for the corresponding electronic device is absolutely necessary. For example, a smartphone requires a charger, a computer has a built-in power supply, and a monitor uses a separate power adapter. That is, at least one power circuit may be provided per one electronic device.

In the past, power circuits were of a relatively simple linear type with inexpensive components, but recently, switching power circuits are mostly used because of their very low power efficiency. The switching power circuit is divided into an isolated type and a non-isolated type. In the non-isolated switching power circuit, a buck circuit that lowers the voltage, a booster circuit that increases the voltage, and an inverter that generates a negative voltage ) circuit.

1 is a diagram showing an example of an insulated switching power supply circuit.

The insulated switching power circuit may be configured as shown in FIG. 1 , and converts power of a high voltage such as 220V to a low voltage.

Referring to FIG. 1 , when a high voltage alternating current is input to an insulated switch power circuit, the input high voltage alternating current is converted into direct current through a rectifier circuit and a filter circuit. For example, when an alternating current of 220V is rectified, a direct current of about 311V, which is twice the route, may be generated. The generated direct current is converted into a high-frequency alternating current of several hundred kHz through a switching transistor, and then converted into a desired voltage through a transformer. The AC converted to a desired voltage is rectified again using a high-speed diode such as a Schottky diode, and the rectified AC passes through a filter circuit composed of an inductor and a capacitor to generate a complete low-voltage DC.

In the insulated switching power circuit of FIG. 1 as described above, since the high voltage primary side and the low voltage secondary side are electrically insulated by a transformer, it is possible to obtain a safe power from the point of view of a user using the power output to the secondary side. Such an insulated switching power circuit is applied to power supplies of computers, cell phone chargers, general adapters, and general home appliances such as televisions, due to insulation stability.

In the insulated switching power supply circuit of FIG. 1, when rectifying the AC output from the transformer, the negative voltage can be easily obtained by connecting the diode in the reverse direction.

2 is a diagram illustrating an example of a non-isolated switching power supply circuit.

Referring to FIG. 2, the non-isolated switching power circuit is a form in which the transformer is omitted from the insulated switching power circuit of FIG. 1, and since the primary side and the secondary side are not insulated, the primary side voltage is relatively safe For example, it can be used to generate a direct current of a different voltage using a direct current output from another adapter.

3 is a diagram illustrating an example of a buck circuit, and FIG. 4 is a diagram illustrating an example of pulse width modulation (PWM) switching.

In the non-isolated switching power supply circuit, a Buck circuit that generates a current of a voltage lower than the voltage of the input current (Step-Down), There is a booster circuit and an inverter circuit that generates a negative voltage. Among these non-isolated switching power circuits, a buck circuit may be configured as shown in FIG. 3 .

Referring to FIG. 3 , the input DC voltage V _i is applied to the transistor Q1, and the transistor Q1 is switched by the switching circuit. In this case, the switching circuit may switch the transistor Q1 with a pulse width modulation waveform as shown in FIG. 4 .

Referring to FIG. 4 , (a), (b), and (c) three waveforms all have the same frequency, but an on time and an off time are different. That is, in (b) of FIG. 4 , the on time and the off time are almost the same, so that the average voltage is intermediate. 4(b), in FIG. 4(a), the on-time is short and the off-time is long, so the average voltage is low, and in FIG. 4(c), the on-time is long and the off-time is short, so the average voltage this rises

In accordance with the same principle, the waveform of the switching voltage is averaged by the inductor L and the capacitor C in Fig. 3 appears as an output voltage V _o, an output voltage V _o is can never be larger than the input voltage V _i. And, so that the output voltage _Vo is always maintained at a constant voltage, it is fed back to the detection circuit to detect whether it is a target voltage, and accordingly, the switching circuit can adjust the pulse width modulation waveform.

5 is a diagram illustrating a role of a diode in the buck circuit of FIG. 3 .

Referring to FIG. 5 , when the transistor Q1 is turned on, as shown in FIG. 5A , the current Ion flows into the inductor L and the capacitor C instead of flowing through the diode D to be charged, thereby generating an average voltage.

On the other hand, when the transistor Q1 is turned off, the current flowing through the inductor L has inertia and has a property of continuing to flow for a while. So, if there is no diode D, the inductor L tries to forcibly draw current from the transistor Q1, so a strong negative voltage is formed at the collector of the transistor Q1, which may destroy the transistor Q1.

Therefore, when the diode D is installed as shown in FIG. 5(b), a current path is formed so that the current remaining in the inductor L flows smoothly, and the current remaining in the inductor L is also utilized for output. Power efficiency can also be greatly improved. Here, since the diode D has a switching frequency of several tens of kHz or more, a general diode cannot be applied, but a high-speed Schottky diode can be applied.

6 is a diagram illustrating a voltage converter for a vehicle cigar as an example of use of a buck circuit.

Referring to FIG. 6, (a) of FIG. 6 shows the front side of the substrate on which a Schottky diode, an inductor, a capacitor, etc. are disposed, and (b) of FIG. shows the back side of the board. Here, the buck device may be an IC called LM2576.

Such a buck circuit is used to convert an input DC voltage into a lower voltage. For example, the buck circuit may be used for a purpose such as generating a direct current of 5V from a direct current of 12V to 15V, which is a general voltage of a vehicle.

7 is a diagram illustrating an example of an inverter circuit, and FIG. 8 is a diagram illustrating an operation of the inverter circuit of FIG. 7 .

Referring to FIG. 7 , the inverter circuit generates a negative voltage (-V _o ).

Referring to FIG. 8 , when the transistor Q1 is on, current flows to the ground through the inductor L as shown in FIG. 8A , and the current is charged in the inductor L through this.

Thereafter, when transistor Q1 is turned off, current flows continuously from the top of inductor L to the bottom of inductor L due to the property that the charged current continues to flow through inductor L, but since transistor Q1 is off, current flows from capacitor C via diode D pulled out Thus, a negative voltage is charged to the upper end of the capacitor C. That is, when the process of (a) and (b) of FIG. 8 is repeated at a high speed, a negative voltage is continuously generated at the _{output terminal V o .}

9 is a diagram illustrating an example of an inverter circuit using a buck element.

As shown in Fig. 9, an LM2576 element is applied as a buck element to the inverter circuit.

Referring to FIG. 9 , FIG. 9A shows an inverter circuit illustrating an example of generating a voltage of +12V. That is, when an input voltage is applied to pin 1 of the LM2576 device, an output voltage is generated to pin 2 of the LM2576 device. _{The output voltage V o} is generated by the smoothing circuit composed of the Schottky diode D1, the inductor L1, and the capacitor C1. Looking at the output terminal (V _o ), the (+) point becomes +12V based on the (-) point, which is the ground. If the (+) point is assumed to be the ground, the (-) point may be -12V based on the (+) point, which is the ground, and thus may be configured as shown in FIG. 9(b).

That is, in the circuit of Fig. 9 (b), the LM2576 device always maintains +12V between the 3rd pin (ground) and 4th pin (detection), and when the 4th pin is connected to the ground, the LM2576 device Pin 3 (ground) can be used as -12V.

Non-isolated switching power supply circuit devices are mainly produced as two types of dedicated ICs: a buck device and a booster device. Among them, the buck device has a very wide range of uses and produces much more, so the price is very low. For example, in the case of the LM2576 series, which has recently been released from use and mass-produced by various manufacturers, the buck element (LM2576) is in the 300 won range, but the booster element (LM2577) is in the 4800 won range, and the inverter element is similarly priced at 10 bucks. It is more than double the price. Therefore, if the inverter circuit is configured using the buck element, a very large cost reduction effect may occur. However, the inverter circuit to which the buck element is applied is rarely used because there is a problem in that it does not operate and is damaged only by generating a great deal of heat, or is damaged in a short time even if it operates.

10 is a diagram illustrating in detail the configuration of a buck device in an inverter circuit using a buck device, and FIG. 11 is a diagram illustrating an output waveform of each configuration of the buck device of FIG. 10 .

Referring to FIG. 10 , the overcurrent blocking circuit U101 forcibly blocks the overcurrent, U103 generates a reference voltage, and U102 is a differential amplifier that compares the reference voltage and the output voltage. And, U104 is a sawtooth wave oscillator for generating a pulse width modulated waveform, U105 is a comparator that generates a pulse width modulated waveform using the compared voltage and sawtooth wave, and Q101 is a pulse width modulated waveform that outputs the generated pulse width modulated waveform as a strong current. It is a transistor.

Referring to FIG. 11 _{, the difference between the reference voltage V ref} and the feedback voltage (=output voltage) V _f is detected by the differential amplifier U102, and the detected differential voltage V _pwm may be output. Therefore, the differential voltage V _pwm can be expressed by the following equation.

That is, as the feedback voltage V _f is lower _{than the reference voltage V ref , the differential voltage V pwm} has a larger value, and when the two voltages are the same, only α remains and a basic pulse width modulation waveform may be output.

The differential voltage V _pwm is compared with the sawtooth wave V _osc , and the same output voltage as _{V b} of FIG. 11A is generated. At this time, as the load increases and the output voltage decreases, a pulse width modulation waveform in which one cycle of _{V b increases is generated as shown in FIG. 11B .} Then, V _b is applied to the transistor Q101 and outputted to the outside. As a result, as the final voltage decreases, as shown in FIG. 11B , the on-time of the transistor Q101 increases, so that greater power can be supplied.

12 is a diagram illustrating an example of an inverter circuit using a buck element for generating a negative voltage, and FIG. 13 is a diagram illustrating an operation of the inverter circuit of FIG. 12 .

Referring to FIG. 12 , assuming that the buck element U1 is an element that outputs +12V and is in a normal state, the buck element U1 controls the output voltage V _f to _{be +12V higher than V gnd} , so if the output voltage V _f is 0V When grounded as , V _gnd can be -12V.

Referring to FIG. 13, (a) of FIG. 13 is a case in which the transistor Q101 of the buck element U1 is on, and a current flows from the transistor Q101 to the ground through the inductor L1, and accordingly, the inductor L1 is charged with the current.

Thereafter, when the transistor Q101 is turned off, as shown in FIG. 13B , the inertial current flowing through the inductor L1 flows from the capacitor C1 through the Schottky diode D1, so that the lower side of the capacitor C1 is charged with a negative voltage.

And, as the processes of FIGS. 13A and 13B are continuously repeated, a negative voltage may be maintained at the lower side of the capacitor C1.

As such, when a negative voltage is generated at the lower side of the capacitor C1, V _gnd of the buck element U1 is set to a negative voltage. That is, since the voltage reference point of the buck element U1 is negative, the feedback voltage V _f becomes a relatively high voltage compared to the negative voltage reference point even though it is 0V, and control is performed to continuously maintain this voltage state.

However, the operation as shown in FIG. 13 is when the inverter circuit using the buck element is in a normal state, and a problem occurs in the initial state when power is first applied to the inverter circuit using the buck element.

14 is a diagram illustrating an initial state immediately after power is first applied to an inverter circuit using a buck element.

Figure 14 (a) shows the voltage state immediately after the first power is supplied to the inverter circuit using the buck element. Referring to (a) of FIG. 14 , even when the input voltage V _i is applied, the upper side of the capacitor C1 is connected to the ground so that it is 0V, and the lower side of the capacitor C1 does not have a charged voltage because the circuit operation has not been performed yet. not 0V. _{This means that V gnd} of the buck element U1 is also 0V.

In the buck element U1, since the feedback voltage V _f is 0V, the differential amplifier U102 compares the reference voltage V _ref and the feedback voltage V _f , and a very large difference occurs, and the differential voltage V _pwm is set as shown in (b) of FIG. 14 . Set the largest together. In this case, as shown in (b) of FIG. 14 , V _b is output to the transistor Q101 and the transistor Q101 is kept on, so that a large current can flow through the inductor L1 to increase the output voltage. However, since the upper side of the capacitor C1 is connected to ground, the feedback voltage V _f can never rise, so that the transistor Q101 remains on and the buck element U1 continues to output current.

As described above with reference to FIG. 13 , a negative voltage may be charged to the lower side of the capacitor C1 when the transistor Q101 is turned off. However, in the initial state as shown in FIG. 14 , the transistor Q101 is not turned off, so that a negative voltage is not generated at the lower side of the capacitor C1.

Accordingly, when an overcurrent flows through the transistor Q101 and the overcurrent blocking circuit U101 operates and the circuit is opened, the operation as shown in FIG. 13B can be achieved only at that time.

Consequently, if the transistor Q101 is turned off even once, a negative voltage is generated at the lower side of the capacitor C1. _{Accordingly, V gnd, which} is the reference voltage of the entire buck element U1, drops to negative, and the reference voltage V _ref drops. Since this is a relatively _{increased feedback voltage V f} , the inverter circuit may enter a steady state.

As such, in the inverter circuit using the buck element, a negative voltage is generated only when the current flowing to the inductor L1 is cut off at least once. can work

However, the operation of the overcurrent blocking circuit means that too much current flows into the buck element, which is a dangerous situation, and the buck element is damaged.

Therefore, when the inverter circuit is operated in this way, there is a risk that the buck element is damaged every time the power is turned on. In fact, the buck element of the inverter circuit is damaged in less than one-tenth of the expected lifespan, and in the field, when constructing an inverter using the buck element, a socket for detaching the buck element is used to replace the frequently damaged buck element. It is being applied.

15 is a diagram illustrating a case in which an inverter circuit receives power from another power supply circuit.

The problem of starting using the overcurrent of the inverter circuit using the buck element may occur most seriously when power is supplied from another power supply circuit, as shown in FIG. 15 .

Referring to FIG. 15 , when power (+12V, 3A) is supplied into the device from another power supply circuit, power such as +12V originally required inside the device and +5V, -12V to be used in other devices is supplied to the device’s power circuit. creates At this time, since the +5V power can be generated by lowering the +12V power supplied from the outside, a buck circuit can be applied. However, in order to generate a power of -12V, an inverter circuit using a buck circuit must be applied. When the inverter circuit using the buck circuit is operated, the entire device is paralyzed, and there is a risk of fire even occurring in the device.

16 is a diagram illustrating an example of an inverter circuit using a buck element to solve a withstand voltage problem.

Referring to FIG. 16 , the inverter circuit of FIG. 16 includes a circuit configured to be input as a _{feedback voltage V f} by inverting an output voltage using an operational amplifier U2 to the inverter circuit using the above-described buck element.

For example, the input voltage is 36V and V _i, when the output voltage is -12V, the voltage applied between the Buck device U1, the input voltage V _i and V is the _gnd is up to 48V may damage the Buck device U1. Thus, even in the inverter circuit 16, the input voltage V _i will be configured to be configured such that after the true output inverter circuit while maintaining the V between the _gnd to 36V, the output voltage feedback is inverted in the inverting amplifier.

However, in the inverter circuit diagram of FIG. 16, immediately after power is turned on, the output voltage is 0V, so even if inverted, the output voltage is 0V. Therefore, the problem of starting using overcurrent still exists.

An object of the present invention is to provide an inverter using a microcontroller that generates negative voltage power by starting the buck device even when no overcurrent is applied to the buck device.

According to one aspect of the present invention, an inverter using a microcontroller for generating a negative voltage power supply is disclosed.

An inverter using a microcontroller according to an embodiment of the present invention includes a buck element, an inductor having one end connected to an output voltage pin of the buck element, a first diode having one end connected to the output voltage pin, and the inductor A first capacitor to which the other side and the positive pole are connected, a first connection point formed by connecting the other side of the inductor to the positive pole of the first capacitor, a ground pin of the buck element, the other side of the first diode, and the first capacitor a second connection point formed by connecting the negative pole of A transistor connected to the ground and a microcontroller connected to a base of the transistor by a first output pin, and connected to the first connection point and the second connection point by a first input pin and a second input pin, respectively However, the microcontroller controls the switching of the transistor through the first output pin according to voltage values of the first connection point and the second connection point.

In the inverter using the microcontroller, a first resistor connected between the base and the first output pin, a second resistor connected between the first connection point and the first input pin, one side of the first input pin is a third resistor connected and the other end connected to the ground, a fourth resistor connected between the second connection point and the second input pin, one end connected to the second input pin, and the other end connected to a power source more resistance.

The microcontroller, when the voltage value of the first connection point is equal to or greater than a preset normal voltage value, outputs a value of 1 to the first output pin so that the transistor is turned on and the first connection point is connected to the ground.

The microcontroller performs a time delay for a preset time in order to secure a time when the transistor is turned on and a time when the inverter circuit operation is stabilized.

The microcontroller, when the voltage value of the second connection point is equal to or greater than a preset negative voltage value, the transistor is turned off to block the output of the negative voltage in order to prevent the voltage from rising due to the overcurrent of the load using the negative voltage. As much as possible, a value of 0 is output to the first output pin.

The inverter using the microcontroller further includes a light emitting diode connected in series to a second output pin of the microcontroller, a sixth resistor and a ground, a switch connected in series to a third input pin of the microcontroller, and a ground .

When the voltage value of the second connection point is equal to or greater than a preset negative voltage value, the microcontroller outputs a value of 1 to the second output pin so that the light emitting diode is turned on, in order to inform that the output of the negative voltage is cut off, When the switch is on, a value of 0 is output to the second output pin so that the light emitting diode is turned off in order to inform that the switch is on.

In the inverter using a microcontroller according to an embodiment of the present invention, the buck element is started even when no overcurrent is applied to the buck element to generate a negative voltage power supply, so that an inexpensive buck element can be stably applied to the inverter. It is possible to reduce the manufacturing cost of the power circuit of the electronic device.

1 is a diagram showing an example of an insulated switching power supply circuit.
2 is a diagram showing an example of a non-isolated switching power supply circuit.
3 is a diagram showing an example of a buck circuit;
4 is a diagram illustrating an example of pulse width modulation (PWM) switching.
5 is a view showing the role of a diode in the buck circuit of FIG.
6 is a diagram illustrating a voltage converter for a vehicle cigar as an example of use of a buck circuit.
7 is a diagram showing an example of an inverter circuit;
Fig. 8 is a view showing the operation of the inverter circuit of Fig. 7;
9 is a diagram showing an example of an inverter circuit using a buck element.
10 is a diagram illustrating in detail the configuration of a buck element in an inverter circuit using the buck element;
11 is a diagram illustrating an output waveform of each configuration of the buck element of FIG. 10 .
12 is a diagram showing an example of an inverter circuit using a buck element that generates a negative voltage.
Fig. 13 is a view showing the operation of the inverter circuit of Fig. 12;
14 is a view illustrating an initial state immediately after power is first applied to an inverter circuit using a buck element.
15 is a diagram illustrating a case in which an inverter circuit receives power from another power supply circuit;
16 is a view showing an example of an inverter circuit using a buck element for solving a withstand voltage problem.
17 is a diagram showing a circuit of an inverter using a microcontroller according to an embodiment of the present invention.
Fig. 18 is a diagram for explaining the inverter circuit of Fig. 17;
19 is a flowchart illustrating an operation method of the microcontroller in the inverter circuit of FIG. 17;

As used herein, the singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as “consisting of” or “comprising” should not be construed as necessarily including all of the various components or various steps described in the specification, some of which components or some steps are It should be construed that it may not include, or may further include additional components or steps. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. .

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

17 is a diagram illustrating a circuit of an inverter using a microcontroller according to an embodiment of the present invention, and FIG. 18 is a diagram for explaining the inverter circuit of FIG. 17 .

Referring to FIG. 17 , an inverter using a microcontroller according to an embodiment of the present invention includes a buck element U1, a diode D1, an inductor L1, a capacitor C1, a diode D2, a transistor Q1, a microcontroller U2, a resistor R1, a resistor R2, a resistor. R3, resistor R4, resistor R5, resistor R6, may include a light emitting diode (LED1) and a switch (SW1).

Buck device U1 is an LM2576 IC and includes five pins: an input voltage pin (V _in ), an output voltage pin (V _out ), a ground pin (GND), an enable pin (OE), and a feedback pin (Feedback).

One side of the inductor L1 and the forward side of the diode D1 are connected to the output voltage pin (V _{out ) of the buck element U1.} That is, the diode D1 has a forward direction from the other side to one side.

In addition, the other side of the inductor L1 and the positive pole of the capacitor C1 are connected, and a first connection point formed by connecting the other side of the inductor L1 and the positive pole of the capacitor C1 becomes an output terminal. A first connection point serving as an output terminal is connected to a feedback pin (Feedback) of the buck element U1.

Meanwhile, the ground pin GND and the activation pin OE of the buck element U1, the other side of the diode D1, and the negative pole of the capacitor C1 are connected to form a second connection point.

A diode D2 is connected between the formed second connection point and the ground. In this case, the diode D2 may be connected so that the direction from the second connection point to the ground is forward.

A transistor Q1 is connected to a first connection point serving as an output terminal. That is, the collector of the transistor Q1 is connected to the first connection point, and the emitter is connected to the ground.

Then, the first connection point, the second connection point, and the base of the transistor Q1 are connected to the microcontroller U2 as shown in FIG. 17 .

Referring to FIG. 17 , the microcontroller U2 has a first analog pin (AN0), a second analog pin (AN1), a first output pin (output port 0), a second output pin (output port 1), and an input pin (input). port 0).

So, the first connection point is connected to the first analog pin AN0 of the microcontroller U2, the second connection point is connected to the second analog pin AN1 of the microcontroller U2, and the base of the transistor Q1 is the second analog pin AN0 of the microcontroller U2. 1 It is connected to the output pin (output port 0).

At this time, the resistor R2 and the resistor R3 are connected between the first connection point and the first analog pin, the resistor R4 and the resistor R5 are connected between the second connection point and the second analog pin, and the base of the transistor Q1 and the first output pin ( A resistor R1 is connected between the output ports 0).

Here, both ends of the resistor R2 are connected to the first connection point and the first analog pin AN0 of the microcontroller U2, respectively, and the resistor R3 has one end connected to the first analog pin AN0 and the other end connected to the ground.

In addition, both ends of the resistor R4 are connected to the second connection point and the second analog pin AN1 of the microcontroller U2, respectively, and the resistor R5 has one end connected to the second analog pin AN1 and the other end connected to the power source.

In addition, both ends of the resistor R1 are connected to the base of the transistor Q1 and the first output pin (output port 0), respectively.

To the second output pin (output port 1), a light emitting diode (LED1), a resistor R6, and a ground are connected in series in this order.

To the input pin (input port 0), the switch SW1 and the ground are connected in series in this order.

The microcontroller U2 controls the switching of the transistor Q1 through the first output pin (output port 0) connected to the base of the transistor Q1.

Since all the current flowing to the second connection point flows to the ground by the diode D2, the buck element U1 may operate in a form in which the ground pin GND is connected to the ground during initial operation. Thereafter, when the transistor Q1 is turned on, a negative voltage is generated at the negative pole of the capacitor C1. Accordingly, the diode D2 has a reverse direction and no current flows.

The initial output voltage output from the buck element U1 appears at the positive pole (the first connection point) of the capacitor C1. It is applied to the collector of the transistor Q1 and, on the one hand, is adjusted to a voltage range recognizable by the microcontroller U2 via a voltage divider resistor consisting of resistors R2 and R3 and is input to the first analog pin AN0 of the microcontroller U2. do.

On the other hand, the negative voltage finally generated appears at the negative pole (second connection point) of the capacitor C1. This is adjusted to a voltage range recognizable by the microcontroller U2 through a voltage divider resistor composed of resistors R4 and R5, and is input to the second analog pin AN1 of the microcontroller U2.

The light emitting diode LED1 and the resistor R6 are configured to warn the user through light emission when the output voltage of -12V rises significantly due to overload and reaches a short-circuit state reaching 0V.

The switch SW1 is a switch that receives a recovery command from the user so that it can be restarted normally after the user takes action on an abnormal situation due to overcurrent.

The microcontroller U2 monitors the operation state of the buck element U1 through the first analog pin (AN0) and when it is confirmed that the normal state has entered, the transistor Q1 is turned on at that time, so that a sufficiently long time is secured for a stable operation time. no need to do That is, the switching is performed according to the operating state of the buck element, not according to time, so that the inverter circuit can be operated in the shortest time, and a large-capacity capacitor can be omitted.

In the inverter circuit using the buck element, a current may flow into the negative pole of the capacitor C1 due to a load using a negative voltage, and thus the voltage of the negative pole of the capacitor C1 may increase. This is controlled so that the buck element U1 maintains a normal voltage. This is the opposite principle to that, in a circuit generating a positive voltage, a current flows to a load using the positive voltage and the positive voltage falls.

At this time, when a current in a range that the buck element U1 cannot control, that is, an overcurrent flows due to a circuit failure or other factors in a load using a negative voltage, the voltage continues to rise and finally rises to 0V, the buck element U1 operates Otherwise, it may reach a dangerous state in which only overcurrent flows. In the case of an inverter circuit composed only of passive elements, it cannot cope with the dangerous state caused by such overcurrent, so it can fall into a large dangerous state.

In contrast, in the case of an inverter using a microcontroller according to an embodiment of the present invention, since the microcontroller U2 continuously monitors the negative voltage through the second analog pin AN1, it is determined that a dangerous state due to overcurrent has been reached. Then, transistor Q1 can be turned off to stop the output of the negative voltage. In addition, the microcontroller U2 may notify the user of this situation through light emission of the light emitting diode LED1.

Inverter using a microcontroller according to an embodiment of the present invention is configured by further adding a microcontroller U2. It can be configured using the pins of

Alternatively, since a microcontroller is not applied to an electronic device, when a microcontroller only for an inverter using a microcontroller according to an embodiment of the present invention is added, since there are only 5 ports to control, an 8-pin microcontroller (eg, ATtiny13A, etc.) can be configured.

Accordingly, the inverter using the microcontroller according to the embodiment of the present invention can be manufactured inexpensively.

Hereinafter, a circuit design of an inverter using a microcontroller according to an embodiment of the present invention will be described.

Typically, it is assumed that the microcontroller uses a power supply of +5V. Further, assuming that the transistor Q1 processes up to 3A and the current amplification of the transistor Q1 is 150, the base current of the transistor Q1 should be at least greater than the value calculated by the following equation.

An offset voltage of 0.6V of the transistor Q1 is applied to the left side of the current limiting resistor R1, and an output +5V of the first output pin (output port 0) of the microcontroller U2 is applied to the right side of the resistor R1. Therefore, the maximum resistance value of the resistor R1 can be calculated by the following equation.

The resistors R2 and R3 adjust the voltage generated during the initial operation of the buck element U1 to a voltage range recognizable by the microcontroller. When the buck element U1 is for 12V, it can be represented as shown in FIG. 18(a).

When the input voltage of the resistor R2 is +12V, in order for the maximum voltage of the microcontroller U2 to be output to the first analog pin AN0 of +5V, the resistance ratio of the resistors R2 and R3 can be calculated as shown in the following equation.

That is, the resistance of the resistor R2 is 1.4 times that of the resistor R3. Since this has completely reached the maximum voltage of the microcontroller +5V, if you want to leave a margin smaller than this, you can set the resistance value of the resistor R2 to be 1.4 times higher than that of the resistor R3.

For example, the resistor R3 can be set to 10KΩ, and the resistor R2 can be set to 15KΩ, which is 1.5 times the resistor R3. In this case, when the input voltage is +12V, the voltage transferred to the first analog pin AN0 of the microcontroller U2 may be the value of the following equation.

The resistors R4 and R5 adjust the negative voltage to a voltage range recognizable by the microcontroller, and when the output of the inverter circuit is -12V, it can be represented as shown in FIG. 18(b).

The second analog pin AN1 becomes the minimum voltage of 0V, and if -12V rises, the voltage of the second analog pin AN1 also increases. Therefore, in order to output the minimum voltage 0V of the microcontroller U2 to the second analog pin AN1, the resistance ratio of the resistors R4 and R5 can be calculated as shown in the following equation.

In consideration of the margin of voltage, the resistance value of resistor R4 should be set to be 2.4 times or more of resistor R5. For example, resistor R5 can be set to 10KΩ, and resistor R4 can be set to 25KΩ, which is 2.5 times the resistor R5. In this case, when the input voltage is +12V, the voltage transferred to the second analog pin AN1 of the microcontroller U2 may be the value of the following equation.

If the input voltage is +0.6V, which is the initial state of the buck element U1, the voltage transferred to the second analog pin AN1 may be calculated as shown in the following equation.

That is, both the voltage values of Equations 7 and 8 satisfy the voltage range of the microcontroller.

19 is a flowchart illustrating an operation method of the microcontroller in the inverter circuit of FIG.

First, the microcontroller sets the provided pins when the power is turned on and a reset occurs. That is, the microcontroller can set each pin as an input port or an output port, and set the initial value of each pin.

Next, the microcontroller converts the analog voltage value of the voltage applied to the first analog pin AN0 to a digital value in order to check whether the output voltage of the buck element U1 has risen to a preset normal voltage value (eg, 11V). convert to

Next, the microcontroller determines whether the voltage value of the voltage applied to the first analog pin AN0 is equal to or greater than a preset normal voltage value, and when the voltage value is equal to or greater than the preset normal voltage value, the first transistor Q1 is turned on. Output 1 value to the output pin (output port 0).

Next, the microcontroller delays the time in order to secure the time when the transistor Q1 is turned on and the time when the operation as an inverter circuit is stabilized. For example, a microcontroller can delay a time of about 2 ms or more. Assuming that the operating frequency of the buck element U1 is 50 kHz, a time delay of 2 ms is sufficient. If the time delay is not performed, an operation of blocking the circuit by detecting an overcurrent state may occur because the inverter circuit is not yet stabilized.

Next, since the microcontroller operates as an inverter circuit as the transistor Q1 is turned on, the analog voltage value of the voltage applied to the second analog pin AN1 is converted into a digital value in order to check the state of the negative voltage. .

Next, the microcontroller determines whether or not the voltage value of the voltage applied to the second analog pin AN1 is greater than or equal to a preset negative voltage value (eg, -11V), and if greater than or equal to the preset negative voltage value, Since the voltage is increased due to the overcurrent of the load using the negative voltage, a value of 0 is output to the first output pin (output port 0) so that the transistor Q1 is turned off to block the output of the negative voltage.

Next, the microcontroller outputs a value of 1 to the second output pin (output port 1) so that the light emitting diode LED1 is turned on in order to inform the user that the output of the negative voltage is cut off.

Thereafter, the microcontroller determines whether the switch SW1 is turned on by the user, and when the switch SW1 is turned on, the light emitting diode LED1 is turned off to notify the user that the switch SW1 is turned on. A value of 0 is output to the second output pin (output port 1) as much as possible.

Next, in order to remove the chattering phenomenon occurring in the switch SW1, the microcontroller performs debounce with a delay of about 20-100 ms.

Next, the microcontroller waits until the switch SW1 is turned off, and then enters the initial state 1 again when the switch SW1 is turned off.

The above-described embodiments of the present invention are disclosed for purposes of illustration, and various modifications, changes, and additions will be possible within the spirit and scope of the present invention by those skilled in the art having ordinary knowledge of the present invention, and such modifications, changes and additions should be regarded as belonging to the following claims.

Claims (7)

In an inverter using a microcontroller for generating a negative voltage power source,
Buck element;
an inductor having one end connected to an output voltage pin of the buck element;
a first diode having one end connected to the output voltage pin;
a first capacitor to which the other side of the inductor and a positive pole are connected;
a first connection point formed by connecting the other side of the inductor and the positive electrode of the first capacitor;
a second connection point formed by connecting a ground pin of the buck element, the other side of the first diode, and a negative pole of the first capacitor;
a second diode having one end connected to the second connection point and the other end connected to the ground;
a transistor having a collector connected to the first connection point and an emitter connected to ground; and
a microcontroller connected to the base of the transistor by a first output pin and connected to the first and second connection points by a first input pin and a second input pin, respectively;
the first diode is connected such that a direction from the second connection point to the output voltage pin is forward;
The second diode is connected so that the direction from the second connection point to the ground is forward;
wherein the microcontroller controls the switching of the transistor through the first output pin according to voltage values of the first connection point and the second connection point.
According to claim 1,
Inverter using the microcontroller,
a first resistor coupled between the base and the first output pin;
a second resistor connected between the first connection point and the first input pin;
a third resistor having one end connected to the first input pin and the other end connected to the ground;
a fourth resistor connected between the second connection point and the second input pin;
The inverter using a microcontroller, characterized in that it further comprises a fifth resistor having one end connected to the second input pin and the other end connected to a power source.
According to claim 1,
When the voltage value of the first connection point is greater than or equal to a preset normal voltage value, the microcontroller outputs a value of 1 to the first output pin so that the transistor is turned on and the first connection point is connected to the ground. Inverter using a microcontroller.
4. The method of claim 3,
The microcontroller is an inverter using a microcontroller, characterized in that the time delay is performed by a preset time in order to secure a time for which the transistor is turned on and a time for stabilizing the inverter circuit operation.
5. The method of claim 4,
The microcontroller, when the voltage value of the second connection point is equal to or greater than a preset negative voltage value, the transistor is turned off to block the output of the negative voltage in order to prevent the voltage from rising due to the overcurrent of the load using the negative voltage. Inverter using a microcontroller, characterized in that outputting a value of 0 to the first output pin as much as possible.
According to claim 1,
Inverter using the microcontroller,
a light emitting diode connected in series to a second output pin of the microcontroller, a sixth resistor and ground;
Inverter using a microcontroller, characterized in that it further comprises a switch and ground connected in series to the third input pin of the microcontroller.
7. The method of claim 6,
The microcontroller is
When the voltage value of the second connection point is equal to or greater than a preset negative voltage value, a value of 1 is outputted to the second output pin so that the light emitting diode is turned on in order to inform that the output of the negative voltage is cut off,
Inverter using a microcontroller, characterized in that when the switch is on, outputting a value of 0 to the second output pin so that the light emitting diode is turned off in order to inform that the switch is on.

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